Dock levelers are mounted on loading docks and are adapted to bridge the gap between the dock and the end of a vehicle (e.g., a truck) parked in front of the dock. The dock leveler enables material handling equipment, such as a fork lift, to move between the dock and the vehicle bed.
The typical dock leveler includes a supporting structure, which is mounted in a pit in the loading dock, and a ramp. The rear end of the ramp is pivotally attached to the supporting structure so that the ramp is movable from a horizontal position to a position within the working range of the ramp (e.g., between an upwardly inclined position and a downwardly declined position). Hinged to the front end of most ramps is an extension lip, which is movable between a downwardly hanging pendent position and an extended position where the lip forms an extension to the ramp. Typically, after a truck is parked in front of the loading dock in preparation for a loading operation, the ramp of the dock leveler is pivoted upwardly to allow the pendent lip to clear the vehicle bed and subsequently lowered. As the ramp is moved, the lip is pivoted outwardly from the pendent position to the extended position. As the ramp is lowered, the extended lip will engage the bed of the truck to provide support to the ramp.
Many dock levelers also include support legs that maintain the ramp in a substantially horizontal position when the ramp is not in use (i.e., when the dock leveler is not engaged with a truck bed). These legs can be retracted for servicing truck beds that are below dock level. Typically, a pair of support legs are pivotally attached to the ramp at or around the lip hinge area and extend downwardly to engage a supporting sub-frame. The support legs may be spring biased forwardly toward a supporting position, and may be retracted to a non-supporting position by one of several means.
Both manual and automatic mechanisms have been used to retract the support legs. Manual support leg retraction mechanisms require the operator to engage a mechanism, for example by pulling a chain, to retract the support legs as the ramp is being lowered. Automatic support leg retraction mechanisms typically retract the support legs as the lip of the dock leveler is extended. In this way, the support leg is always retracted when the lip engages a truck bed.